If vibration causes nuts to constantly work loose, first add a lock washer, if it doesn't have one. Or, if there is room on the bolt, use two nuts, tightened toward each other so they lock solidly. You can also try wrapping monofilament fishing line under the nut before tightening it on the bolt. Another possibility is to try wrapping the threads first with the teflon tape that is used in plumbing.
When doing tree pruning work, making an extra undercut with your pruning saw will help keep the bark below heavier branches from stripping down and marring the trunk. Make the undercut from below the branch, about 4 to 6 inches out from the trunk. Then cut from the top of the branch, just outside the lower cut. Lastly, use the saw to make a final cut close to the terminal base.